Roughened bond coat and method for producing using a slurry

ABSTRACT

A method of providing a roughened bond coat, for example in a thermal barrier coating system, comprises providing an oxidation-resistant plasma-sprayed layer onto a substrate and disposing a slurry overlayer on the oxidation-resistant plasma-sprayed layer. These steps form a roughened bond coat possessing an uneven, undulated, and irregular surface. A roughened bond coat in a thermal barrier coating system reduces de-bonding of the bond coat and a thermal barrier coating layer, which is desirable to maintain the insulation features of the thermal barrier coating system.

BACKGROUND OF THE INVENTION

[0001] The invention relates to bond coats. In particular, the inventionrelates to roughened bond coats for thermal barrier coating systems.

[0002] Thermal barrier coating systems are used in hot-sectioncomponents in turbine and turbine components, for example components ofjet engines and gas turbines. The thermal barrier coating systeminsulates the turbines from high temperatures during thermal cycling.Thermal barrier coating systems include a thermal barrier coating (TBC)disposed on a bond coat, which in turn is disposed on a substrate. Thethermal barrier coating normally comprises zirconia, for example such asone of a stabilized zirconia and a partially-stabilized zirconia (PSZ).The bond coat typically comprises an oxidation-resistant metallic layerdisposed between the TBC and substrate (turbine component). The TBC isadhered to the bond coat typically by mechanical interlocking, so thebond coat provides oxidation resistant to the substrate and a relativelyrough surface. The bond coat surface generally has Ra (ArithmeticAverage Roughness (Ra) as determined from ANSI/ASME Standard B461-1985)values over about 350 mainly by mechanical interlocking. So the functionof the bond coat is to provide oxidation resistant to the substrate anda relatively rough surface, preferably with Ra values over about 350microinches, for the TBC to adhere to the substrate. Thus, the TBC isdisposed over the turbine component can provide thermal insulation.

[0003]FIG. 1 is a schematic representation of a known thermal barriercoating system 1. A substrate 10 comprises an underlying part of acomponent, for example a turbine component. A bond coat 12 is disposedon the substrate 10. The bond coat is disposed on the substrate 10 byany appropriate method, for example, but not limited to, thermal sprayprocesses, such as vacuum plasma spray (VPS), air plasma spray (APS) andhyper-velocity oxy-fuel (HVOF) spray processes.

[0004] The structure and roughness of bond coat surface 13 are dependenton the spray process. Bond coats deposited by a VPS process aretypically dense and free of oxides. Therefore, VPS-applied bond coatsprovide protection at high temperatures against oxidation. The VPSapplication process disposes fine powders, and thus, VPS-applied bondcoats are typically dense, for example having a density greater thanabout 90% of its theoretical density, but have relatively smoothsurfaces. Consequently, a TBC does not adhere well to a VPS bond coat.

[0005] An air plasma spray (APS) process produces rough bond coatsbecause of large powders used in APS. The large powders possess arelatively high heat capacity; however, the APS-applied bond coatscontain high amounts of oxides. Also, APS-applied bond coats possess arelatively low porosity due to the oxidation environment and lowmomentum of the powders. Although APS-applied bond coats provide betterTBC adhesion due to their roughness, they are more prone to oxidationbecause of their relatively high oxide levels and relatively lowporosity.

[0006] Bond coats deposited by HVOF are sensitive to particle sizedistributions. Dense and oxide-free bond coats can be deposited by HVOFusing very lean conditions (low oxygen amounts) and finer particles, forexample particles with a size about −325+10 μm. The surface roughness ofHVOF-applied bond coats is relatively smooth. Rough bond coats can bedeposited by HVOF using coarser powders, for example particles with asize about −230+325, however a low HVOF flame temperature is needed. Thelow flame temperatures result in the bond coat comprising un-meltedpowders, therefore the coating is porous and less dense.

[0007] A TBC 14 is disposed on the bond coat 12 and forms a surface 15against the surface 13. The TBC 14 is disposed on the bond coat 12 byany appropriate process to adhere (bond) to the bond coat. The TBCsurface 15 and bond coat surface 13 define an interfacial area 16 attheir adjoining surfaces.

[0008] Effectiveness of a thermal barrier coating system during thermalcycling is compromised by de-bonding of the TBC and bond coat, forexample at the TBC and bond coat interfacial area. De-bonding can becaused by at least one of a poor TBC and bond coat adhesion, and lack ofaccommodation of thermal expansion mismatch between the TBC and bondcoat. The lack of adhesion is characteristic of smooth adjoiningsurfaces where a total surface area is minimal. The thermal expansionmismatch between the TBC and bond coat results from differentcoefficients of thermal expansion of the materials used for thesefeatures. If the difference in coefficients of thermal expansion of theadhered elements is large, one element expands much more than the other,and separation and de-bonding occur at the interfacial areas. De-bondingof the TBC and bond coat is undesirable as the insulation effect of thethermal barrier coating system will be lost at TBC separation.

[0009] Therefore, it is desirable to use a very dense and rough bondcoat that provides oxidation resistance and promotes enhanced adhesionbetween the TBC and the bond coat. The adhesion between the TBC and bondcoat can be increased by increasing an area at an interfacial areamating surface of adhered elements. Increasing a roughness of the bondcoat provides an increased area and enhanced mechanical interlockingbetween the bond coat and TBC. Increasing a bond coat's roughness alsoprovides an increased interfacial surface area for accommodation of anythermal mismatch, with respect to non-roughened bond coats.

SUMMARY OF THE INVENTION

[0010] Thus, this invention overcomes the above noted deficiencies ofknown bond coats and thermal barrier coating systems. The inventionprovides a method for providing a dense (for example at least about 95%its theoretical density), roughened bond coat, for example on asubstrate, such as a turbine component, in a thermal barrier coatingsystem. The method comprises providing an oxidation-resistantplasma-sprayed layer onto a substrate; and disposing a slurry overlayeron the oxidation-resistant plasma-sprayed layer to form a roughened bondcoat possessing an uneven, undulated, and irregular surface.

[0011] A dense, (for example at least about 95% its theoreticaldensity), roughened bond coat is also set forth in an embodiment of theinvention. The roughened bond coat comprises an oxidation-resistantplasma-sprayed layer and a slurry overlayer on the oxidation-resistantplasma-sprayed layer to form an uneven, undulated, and irregularsurface.

[0012] Further, a method for providing a thermal barrier coating systemis disclosed in another embodiment of the invention. The thermal barriercoating system comprises a dense (for example at least about 95% itstheoretical density), roughened bond coat and a thermal barrier coatingdisposed on a substrate. The method of providing a thermal barriercoating system comprises disposing a roughened bond coat on thesubstrate and disposing a thermal barrier coating on the roughened bondcoat. The disposing a roughened bond coat comprises providing anoxidation-resistant plasma-sprayed layer onto a substrate and disposinga slurry overlayer on the oxidation-resistant plasma-sprayed layer toform an uneven, undulated, and irregular surface.

[0013] A thermal barrier coating system, as embodied by the invention,comprises a dense (for example at least about 95% its theoreticaldensity), roughened bond coat disposed on a substrate and a thermalbarrier coating disposed on the roughened bond coat. The roughened bondcoat comprises an oxidation-resistant plasma-sprayed layer and a slurryoverlayer on the oxidation-resistant plasma-sprayed layer. These layersform the roughened bond coat possessing an uneven, undulated, andirregular surface.

[0014] These and other aspects, advantages and salient features of theinvention will become apparent from the following detailed description,which, when taken in conjunction with the annexed drawings, where likeparts are designated by like reference characters throughout thedrawings, disclose embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a schematic representation of a known thermal barriercoating system;

[0016]FIG. 2 is a schematic representation of a thermal barrier coatingsystem including a roughened bond coat;

[0017]FIG. 3 is a flow chart of one method for forming a thermal barriercoating system; and

[0018]FIG. 4 is a microphotograph of a roughened bond coat.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Roughened bond coats enhance adhesion between a thermal barriercoating (TBC) and a bond coat in a thermal barrier coating system.Roughened bond coats prevent de-bonding and separation between the TBCand bond coat of the thermal barrier coating system. A roughened bondcoat increases interfacial mating surface areas of adhered elements,enhances mechanical interlocking between the bond coat and TBC, andprovides for accommodation of any thermal mismatch between the TBC andbond coat. Accordingly, expansion of elements in a thermal barriercoating system with a roughened bond coat does not lend to separationand de-bonding therebetween. An effect of the roughened bond coatincludes an enhanced life of the TBC in the thermal barrier coatingsystem.

[0020] In the following description, material compositions of mixturesare provided in weight percent unless otherwise expressed. Further,individual compositions are provided in weight percent, unless otherwiseprovided. For example, if a mixture comprises about 70% of Constituent Aand about 30% of constituent B, the percents are in approximate weightpercents. Nomenclature used for compositions is as follows. IfComposition A comprises Ni-23Cr-6Al-0.4Y, yttrium is provided at 0.4weight percent, aluminum is provided at 6 weight percent, chromium isprovided at 23 weight percent, and nickel is provided as the balanceweight percent.

[0021]FIG. 2 is a schematic illustration of a thermal barrier coatingsystem 100, as embodied by the invention. The thermal barrier coatingsystem 100 comprises a substrate 110. A dense roughened bond coat 120,which possesses an uneven, undulated, and irregular surface, is disposedon the substrate 110. A thermal barrier coating (TBC) 130 is disposed onthe roughened bond coat 120. The roughened bond coat 120 comprises anuneven, undulated, and irregular surface 121, which is disposed againsta mating surface 131 of the TBC 130 to define a roughened interfacialsurface area 140. The density of the bond coat 120 is at least about 95%its theoretical density.

[0022] The substrate 110 comprises an element to be thermally insulatedby the thermal barrier coating system 100. For example, the substrate110 comprises a component such as a turbine component, turbine airfoilblade, bucket, vane, and nozzle (hereinafter “turbine component”). Ifthe substrate 110 comprises a turbine component, an appropriatesubstrate material includes one of a nickel-based superalloy material,an iron-based superalloy material, a nickel-iron-based superalloymaterial, and a cobalt-based superalloy material. The followingdescription refers to a nickel-based superalloy material, however thismaterial is merely exemplary of substrate materials, and is not meant tolimit the invention in any way. Other substrate materials are within thescope of the invention.

[0023] The TBC 130 comprises appropriate materials that provide thermalinsulation. For example, but in no way limiting of the invention, theTBC 130 comprises zirconia. The zirconia comprises at least one of astabilized zirconia and a partially stabilized zirconia (PSZ).

[0024] The roughened interfacial surface area 140, which is defined bythe surfaces 121 and 131, has a larger interfacial surface -8 area, withrespect to a substantially smooth interfacial area 16 of a known thermalbarrier coating system 1. The roughened interfacial surface area 140permits more contact between the roughened bond coat 120 and the TBC130. This contact provides enhanced mechanical interlocking and adhesionbetween the bond coat 120 and TBC 130.

[0025] The roughened bond coat 120 comprises an oxidation-resistantplasma-sprayed layer 122 and a slurry overlayer 124. Theoxidation-resistant plasma-sprayed layer 122 is applied to the substrate110 by an appropriate process, such as by an air plasma-sprayingprocess.

[0026] The oxidation-resistant plasma-sprayed layer 122 comprises anoxidation resistant material. An exemplary oxidation resistant materialcomprises MCrAlY, where M is at least one of nickel (Ni), iron (Fe), andcobalt (Co), for example Ni-23Cr-6Al-0.4Y (weight percent). Theoxidation-resistant plasma-sprayed layer 122 is applied with a thicknessin a range from about 0.005 inches to about 0.010 inches (about 0.0125cm to about 0.025 cm). The invention describes MCrAlY as NiCrAlY,however this is merely exemplary and not meant to limit the invention inany way.

[0027] The roughness of the bond coat 120 is sufficient to increaseinterfacial surface areas at the interface, thus reducing de-bonding andincreasing accommodation of thermal expansion mismatches. The bond coat120, as embodied by the invention, possesses a roughness in a range ofabout 100 microinches (about 2.5×10⁻⁴ cm) Ra (Arithmetic AverageRoughness (Ra) as determined from ANSI/ASME Standard B461-1985) to about2000 microinches (about 5.0×10⁻³ cm) Ra. Alternatively, the bond coat120 possesses a roughness in a range of about 100 microinches (about2.5×10⁻⁴ cm) Ra to about 400 microinches (about 1.0×10⁻³ cm) Ra.Further, the bond coat 120 possesses a roughness in a range of about 100microinches (about 2.5×10⁻⁴ cm) Ra to about 300 microinches (about7.5×10⁻⁴ cm) Ra.

[0028] The slurry overlayer 124 is formed from a slurry mixture. Theslurry mixture comprises at least a first oxidation-resistant powderwith a first melting point, a second oxidation-resistant powder with asecond melting point that is lower than the first melting point, and anappropriate binder that holds powders and similar materials together.The slurry overlayer 124 is disposed on the oxidation-resistantplasma-sprayed layer 122. For example, the slurry overlayer 124 iscoated onto the oxidation-resistant plasma-sprayed layer 122, such as bya painting process. The combination of first and second melting pointpowders results in a higher density, for example a density of at leastabout 95% of its theoretical density.

[0029] Compositions for the slurry overlayer 124 comprise a binder and ametal powder, where the metal powder comprises various constituents invarious amounts. A first slurry composition, “Slurry A” comprises amixture of about 70% metal powder by weight and about 30% binder byweight. The Slurry A metal powder comprises about 50 volume-percentNiCrAlY (Ni-23Cr-6Al-0.4Y) and about 50 volume-percent Al-11.6Si (weightpercent).

[0030] A second slurry composition, “Slurry B,” also comprises a mixtureof about 70% metal powder by weight and about 30% binder by weight. TheSlurry B metal powder comprises about 50 volume-percent NiCrAlY andabout 50 volume-percent Ni-60Al-1B (weight-percent).

[0031] NiCrAlY is an oxidation-resistant material with a relatively highmelting point (about 1350° C.). Al-11.6Si and Ni-60Al-1B have meltingpoints, about 577° C. and about 850° C., respectively, which are lowerthan that of NiCrAlY. Therefore, Al-11.6Si and Ni-60Al-1B melt beforeNiCrAlY during any subsequent heat treatments of the thermal barriercoating system 100. When the Al-11.6Si and Ni-60Al-1B reacts with theNiCrAlY in the slurry and the material of the oxidation resistant layer122 re-solidify, they fuse (bond) the NiCrAlY and layer 122 together.The TBC, for example, but not limited to, a ceramic composition TBC, isthen applied to the surface 121 by an appropriate process, such as, butnot limited to, air plasma spraying (APS)

[0032]FIG. 3 is a flow chart of a process to prepare a thermal barriercoating system that includes a roughened bond coat, as embodied by theinvention. In step S1, the oxidation-resistant plasma-sprayed layer isdisposed onto a substrate, for example a turbine component. In step S2,the slurry overlayer is disposed on the oxidation-resistantplasma-sprayed layer. The disposing of the oxidation-resistantplasma-sprayed layer and slurry overlayer form a bond coat, when theyare re-acted and fused in a heat treatment of step S3. For example, anexemplary heat treatment comprises heating at about 1200° C. for about 1hr in a vacuum.

[0033] In step S4, a TBC is disposed onto the bond coat to form athermal barrier coating system. The thermal barrier coating systemundergoes optional heat treatment in step S5. Any optional heattreatments of the thermal barrier coating system occur after the TBC hasdried.

[0034] Re-solidification after heat treatment causes the melted lowmelting point powder, such as at least one of melted Al-11.6Si andNi-60A-1B, to fuse un-melted high melting point powders, for exampleNiCrAlY powder, to the plasma-sprayed layer. The fusing results in anenhanced roughened bond coat since some un-melted powders tend to belocated at the surface of the material as it re-solidifies. The fusingalso results in enhanced adhesion of the thermal barrier coatingsystem's features because of the enhances interfacial area.

[0035]FIG. 4 is as microphotograph of a roughened bond coat, as embodiedby the invention. As illustrated, a surface of the bond coat is roughand possesses an uneven, undulated, and irregular surface. A highmelting point powder, such as NiCrAlY powder, in the slurry-formedoverlayer does not melt during heat treatment, since its melting pointis higher than that of the heat treatment. If the heat treatmenttemperature is above that of the low melting point powder, such asAl-11.6Si and Ni-60Al-1B, these powders are melted, re-acted, andre-solidified.

[0036] While various embodiments are described herein, it will beappreciated from the specification that various combinations ofelements, variations or improvements therein may be made by thoseskilled in the art, and are within the scope of the invention.

1. A method of providing a bond coat, the method comprising: disposingan oxidation-resistant plasma-sprayed layer on a substrate; anddisposing an overlayer on the oxidation-resistant plasma-sprayed layerto form an uneven, undulated, and irregular surface, where a density ofthe bond coat is at least about 95% its theoretical density.
 2. A methodaccording to claim 1, wherein the step of disposing anoxidation-resistant plasma-sprayed layer comprises air-plasma spraying.3. A method according to claim 1, wherein the step of disposing anoxidation-resistant plasma-sprayed layer comprises plasma spraying anoxidation-resistant material.
 4. A method according to claim 3, whereinthe oxidation resistant material comprises MCrAlY, where M is at leastone of nickel (Ni), iron (Fe), and cobalt (Co).
 5. A method according toclaim 4, wherein the MCrAlY comprises Ni-23Cr-6Al-0.4Y.
 6. A methodaccording to claim 5, wherein said plasma spraying comprises providing alayer with a thickness in a range from about 0.0125 cm to about 0.025cm.
 7. A method according to claim 1, wherein the step of disposing anoverlayer on the oxidation-resistant plasma-sprayed layer comprisesdisposing a slurry mixture on the oxidation-resistant plasma-sprayedlayer.
 8. A method according to claim 7, wherein the step of disposing aslurry mixture comprises providing a metal powder mixture and a binder.9. A method according to claim 8, wherein the step of providing a metalpowder mixture and a binder comprises providing about 70% by weight ofmetal powder and about 30% by weight of a binder.
 10. A method accordingto claim 8, wherein the step of providing a metal powder mixturecomprises providing a first oxidation-resistant powder metal powderhaving a first melting point and a second oxidation resistant powderhaving a second melting point that is lower than the first meltingpoint.
 11. A method according to claim 9, wherein the step of providingthe first oxidation-resistant powder metal powder and the secondoxidation resistant powder comprises providing about 50% by volume ofthe first oxidation-resistant powder and about 50% by volume of thesecond oxidation-resistant powder.
 12. A method according to claim 8,wherein the oxidation resistant powder mixture comprises MCrAlY, where Mis at least one of nickel (Ni), iron (Fe), and cobalt (Co).
 13. A methodaccording to claim 8, wherein the second oxidation resistant powdermixture comprises at least one of Al-11.6Si and Ni-60Al-1B.
 14. A methodaccording to claim 1, further comprising disposing the bond coat on aturbine component.
 15. A method according to claim 1, wherein thedisposing the metallic material forms the uneven, undulated, andirregular surface with roughness in a range from about 2.5×10⁻⁴ cm Ra toabout 5.0×10⁻³ cm Ra.
 16. A method according to claim 1, wherein thedisposing the metallic material forms the uneven, undulated, andirregular surface with roughness in a range from about 2.5×10⁻⁴ cm Ra toabout 10⁻³ cm Ra.
 17. A method according to claim 1, wherein thedisposing the metallic material forms the uneven, undulated, andirregular surface with roughness in a range from about 2.5×10⁻⁴ cm Ra toabout 7.5×10⁻⁴ cm Ra.
 18. A bond coat comprising: an oxidation-resistantplasma-sprayed layer; and an overlayer on the oxidation-resistantplasma-sprayed layer to form an uneven, undulated, and irregularsurface, where a density of the bond coat is at least about 95% itstheoretical density.
 19. A bond coat according to claim 18, wherein theoxidation-resistant plasma-sprayed layer comprises anoxidation-resistant material.
 20. A bond coat according to claim 19,wherein the oxidation resistant material comprises MCrAlY, where M is atleast one of nickel (Ni), iron (Fe), and cobalt (Co).
 21. A bond coataccording to claim 20, wherein the MCrAlY comprises Ni-23Cr-6Al-0.4Y.22. A bond coat according to claim 18, wherein the oxidation-resistantplasma-sprayed layer comprises a layer with a thickness in a range fromabout 0.0125 cm to about 0.025 cm.
 23. A bond coat according to claim18, wherein the overlayer comprises material formed from a slurrymixture.
 24. A bond coat according to claim 23, wherein slurry mixturecomprises a metal powder mixture and a binder.
 25. A bond coat accordingto claim 24, wherein the metal powder mixture and a binder comprisesabout 70% by weight of the metal powder and about 30% by weight of thebinder.
 26. A bond coat according to claim 25, wherein the metal powdermixture comprises a first oxidation-resistant powder metal powder havinga first melting point and a second oxidation resistant powder having asecond melting point that is lower than the first melting point.
 27. Abond coat according to claim 26, wherein the first oxidation-resistantpowder metal powder and the second oxidation resistant powder compriseabout 50% by volume of the first oxidation-resistant powder and about50% by volume of the second oxidation-resistant powder.
 28. A bond coataccording to claim 27, wherein the first oxidation resistant powdercomprises MCrAlY, where M is at least one of nickel (Ni), iron (Fe), andcobalt (Co).
 29. A bond coat according to claim 27, wherein the secondoxidation resistant powder comprises at least one of Al-11.6Si andNi-60Al-1B.
 30. A bond coat according to claim 18, wherein the bond coatis disposed on a turbine component.
 31. A bond coat according to claim18, wherein the disposing the metallic material forms the uneven,undulated, and irregular surface with roughness in a range from about2.5×10⁻⁴ cm Ra to about 5.0×10⁻³ cm Ra.
 32. A bond coat according toclaim 18, wherein the disposing the metallic material forms the uneven,undulated, and irregular surface with roughness in a range from about2.5×10⁻⁴ cm Ra to about 10⁻³ cm Ra.
 33. A bond coat according to claim18, wherein the disposing the metallic material forms the uneven,undulated, and irregular surface with roughness in a range from about2.5×10⁻⁴ cm Ra to about 7.5×10⁻⁴ cm Ra.
 34. A method of providing athermal barrier coating system, the thermal barrier coating systemcomprises a roughened bond coat and a thermal barrier coating disposedon a substrate, the method comprising: disposing a bond coat on thesubstrate; and disposing a thermal barrier coating on the bond coat;wherein the disposing a bond coat comprises: disposing anoxidation-resistant plasma-sprayed layer onto a substrate; and disposingan overlayer on the oxidation-resistant plasma-sprayed layer to form anuneven, undulated, and irregular surface, where a density of the bondcoat is at least about 95% its theoretical density.
 35. A methodaccording to claim 34, wherein the step of disposing anoxidation-resistant plasma-sprayed layer comprises air-plasma spraying.36. A method according to claim 34, wherein the step of disposing anoxidation-resistant plasma-sprayed layer comprises plasma spraying anoxidation-resistant material.
 37. A method according to claim 36,wherein the oxidation resistant material comprises MCrAlY, where M is atleast one of nickel (Ni), iron (Fe), and cobalt (Co).
 38. A methodaccording to claim 37, wherein the MCrAlY comprises Ni-23Cr-6Al-0.4Y.39. A method according to claim 36, wherein said plasma sprayingcomprises providing a layer with a thickness in a range from about0.0125 cm to about 0.025 cm.
 40. A method according to claim 34, whereinsaid disposing an overlayer on the oxidation-resistant plasma-sprayedlayer comprises disposing and thermally re-acting a slurry mixture onthe oxidation-resistant plasma-sprayed layer.
 41. A method according toclaim 40, wherein the step of providing a slurry mixture comprisesproviding a metal powder mixture and a binder.
 42. A method according toclaim 33, wherein the step of providing a metal powder mixture and abinder comprises providing about 70% by weight of metal powder and about30% by weight of a binder.
 43. A method according to claim 41, whereinthe step of providing a metal powder mixture comprises providing a firstoxidation-resistant powder having a first melting point and a secondoxidation resistant powder having a second melting point that is lowerthan the first melting point.
 44. A method according to claim 43,wherein the step of providing the first oxidation-resistant powder metalpowder and the second oxidation resistant powder comprises providingabout 50% by volume of the first oxidation-resistant powder and about50% by volume of the second oxidation-resistant powder.
 45. A methodaccording to claim 43, wherein the first oxidation resistant powdercomprises MCrAlY, where M is at least one of nickel (Ni), iron (Fe), andcobalt (Co), and the second oxidation resistant powder comprises atleast one of Al-11.6Si and Ni-60Al-1B.
 46. A method according to claim34, the method further comprising heat treating, wherein a portion ofthe bond coat melts and, upon re-solidification, joins the bond coat tothe substrate.
 47. A method according to claim 34, wherein the substratecomprises a turbine component.
 48. A method according to claim 34,wherein the disposing the metallic material forms the uneven, undulated,and irregular surface with roughness in a range from about 2.5×10⁻⁴ cmRa to about 5.0×10⁻³ cm Ra.
 49. A method according to claim 34, whereinthe disposing the metallic material forms the uneven, undulated, andirregular surface with roughness in a range from about 2.5×10⁻⁴ cm Ra toabout 10⁻³ cm Ra.
 50. A method according to claim 34, wherein thedisposing the metallic material forms the uneven, undulated, andirregular surface with roughness in a range from about 2.5×10⁻⁴ cm Ra toabout 7.5×10⁻⁴ cm Ra.
 51. A thermal barrier coating system comprising: abond coat disposed on a substrate; and a thermal barrier coatingdisposed on the roughened bond coat, wherein the bond coat comprises: anoxidation-resistant plasma-sprayed layer; and an overlayer on theoxidation-resistant plasma-sprayed layer to form a bond coat thatcomprises an uneven, undulated, and irregular surface, where a densityof the bond coat is at least about 95% its theoretical density.
 52. Asystem according to claim 51, wherein the oxidation-resistantplasma-sprayed layer comprises an oxidation-resistant material.
 53. Asystem according to claim 52, wherein the oxidation resistant materialcomprises MCrAlY, where M is at least one of nickel (Ni), iron (Fe), andcobalt (Co).
 54. A system according to claim 53, wherein the MCrAlYcomprises Ni-23Cr-6Al-0.4Y.
 55. A system according to claim 51, whereinthe oxidation-resistant plasma-sprayed layer comprises a layer with athickness in a range from about 0.0125 cm to about 0.025 cm.
 56. Asystem according to claim 51, wherein the overlayer comprises materialformed from a slurry mixture.
 57. A system according to claim 56,wherein slurry mixture comprises a metal powder mixture and a binder.58. A system according to claim 57, wherein the metal powder mixture anda binder comprises about 70% by weight of the metal powder and about 30%by weight of the binder.
 59. A system according to claim 58, wherein themetal powder mixture comprises a first oxidation-resistant powder havinga first melting point and a second oxidation resistant powder having asecond melting point that is lower than the first melting point.
 60. Asystem according to claim 59, wherein the first oxidation-resistantpowder and the second oxidation resistant powder comprise about 50% byvolume of the first oxidation-resistant powder and about 50% by volumeof the second oxidation-resistant powder.
 61. A system according toclaim 51, wherein the first oxidation resistant powder comprises MCrAlY,where M is at least one of nickel (Ni), iron (Fe), and cobalt (Co). 62.A system according to claim 51, wherein the second oxidation resistantpowder comprises at least one of Al-11.6Si and Ni60Al-1B.
 63. A systemaccording to claim 62, wherein the system undergoes heat treatment and aportion of the bond coat melts and re-solidifies to join the bond coatto the substrate.
 64. A system according to claim 51, wherein thesubstrate comprises a turbine component.
 65. A system according to claim51, wherein the disposing the metallic material forms the uneven,undulated, and irregular surface with roughness in a range from about2.5×10⁻⁴ cm Ra to about 5.0×10⁻³ cm Ra.
 66. A system according to claim51, wherein the disposing the metallic material forms the uneven,undulated, and irregular surface with roughness in a range from about2.5×10⁻⁴ cm Ra to about 10⁻³ cm Ra.
 67. A system according to claim 51,wherein the disposing the metallic material forms the uneven, undulated,and irregular surface with roughness in a range from about 2.5×10⁻⁴ cmRa to about 7.5×10⁻⁴ cm Ra.
 68. A system according to claim 63, whereinthe substrate comprises a turbine component.